1. Field of the Invention
The present invention relates to a sheath flow forming device and sample analyzer provided with same.
2. Background
A particle analyzer (refer to Japanese Laid-Open Patent Publication No. 9-288053) is a known prior art related to the present invention and includes a container for accumulating a sample liquid containing particles to be analyzed and having a nozzle extending downward from the bottom part, a flow cell into which the tip of the nozzle is inserted, a first pump for injecting into the flow cell a first flow quantity Q1 of a sheath fluid which encapsulates a sample fluid flow injected from the nozzle, and an imaging means for imaging particles in the sample fluid encapsulated in the sheath fluid flowing through a transparent container formed on the downstream side of the flow cell, wherein the top part of the sample fluid container is open to the air, and a second pump is provided for suctioning fluid in the flow cell downstream from the transparent tube path of the flow cell, such that the sample fluid flow quantity Qs is determined by (Q2−Q1) when the injection quantity of the first pump is designated Q1 and the suction quantity of the second pump is designated Q2.
In this conventional device, the sample fluid flow quantity Qs is determined by the difference in the flow quantities of the pumps (Q2−Q1). When one flow quantity changes due to a change in the drive sources of the first and second pumps, the flow quantity Qs fluctuates greatly since the flow quantity Qs is quite small (for example, 1/100) compared to the flow quantities Q1 and Q2. Accordingly, problems arise when this occurs inasmuch as the particle flow in the sample fluid becomes unstable, the measurement accuracy is reduced, and at times measurement becomes impossible.